It is common practice in the construction industry to use flying forms or gang forms in the construction of multifloored buildings such as condominiums and the like. The floor of such buildings extend from supporting walls or columns arranged as a series of bays. A plurality of like forms can be arranged on a ground floor in the bays to provide a first upper form surface. The surface extends from the top of a first wall or column to the top of the next adjacent wall or column. Concrete is poured over the surface and once cured forms a second floor. Walls or columns for the second floor are then constructed while the first floor cures or partially cures. The forms are then removed from under the second floor. The form is then rolled out of the building until approximately 1/3 of the length of the form extends beyond the edge of the floor. A crane is then connected to the form with two front lines, then the form is rolled out until approximately 2/3 of the length of the form extends beyond the edge of the floor. A second set of lines are attached to the form which is then hoisted up and placed on the second floor to act as a platform for pouring the concrete which will form the third floor. The process is repeated until the desired number of floors have been constructed.
The use of such forms have been described in Canadian Patent 941,138. FIG. 1 illustrates the flying forms of Canadian Patent 941,138 which are commercially available under the Trade-mark ALUMA.
Canadian Patent 941,138 discloses a flying form as a concrete forming structure wherein the deck on which the concrete is poured is easily and readily secured to the upper edges of a plurality of beams which are set transversely across a pair of uniform truss members, having a top chord and a lower chord. The truss members are provided with a plurality of screw jacks hingedly secured to the lower chord to present a telescopic leg member. When the structure is to be pulled out and flown, auxiliary jacks such as car jacks are placed under the lower chord, the screw jacks are then swung from beneath the lower chord and secured in an upright position keeping the bottom of the lower chord free of obstruction. Once the screw jacks are in an upright position, the truss is lowered, sometimes 2 feet, to rest on beam rollers to permit the structure to be rolled out of the bay or building.
Flying forms as disclosed in Canadian Patent 941,138 have improved the efficiency of the construction of poured in place concrete buildings. However, such forms require extensive manual labour in manipulating the screw jacks and the leg members and in maneuvering the forms once resting on the floor prior to positioning and in lowering the forms onto rollers so they can be flown from floor to floor.
The prior art form has a height substantially less than the desired height between lower floor and upper floor to be poured to allow the form to pass through openings of a height less than the floor to floor height, for example where a spandrel beam is used. Therefore the form is made in a reduced height to accommodate the reduced opening and therefore must be raised a considerable height before the upper surface of the form is at the desired level.
Elaborate hydraulic jacks have been developed in order for the form to be raised to and lowered from the desired height. However, these hydraulic jacks must be relatively large in order to raise or lower the form and are therefore cumbersome to operate and expensive to manufacture.
Standard hydraulic automobile jacks have been also used to raise or lower the form by placing the standard jacks under the lower chord of the form. This method has proved to be slow with limited success as a uniform height of the upper level of the form is difficult to achieve for the required degree of accuracy. Further, the labour time required to set the forms to the desired height has been high and therefore costly.
The most common procedure is to have the crane hold the form a few feet above the newly poured floor while workers lower the adjusting legs so the form can be set down in approximately the desired position. This procedure requires considerable crane time which is expensive and inefficient.
Once the form has been set to the desired height it is very difficult to move the form if it has not been properly placed. The result is that adjacent forms may not be immediately adjacent to each other or adjacent to the wall leaving irregularly shaped openings in the upper deck of the form. This effect is highly undesirable. Plywood sheets must then be cut for each floor in order to cover these openings prior to pouring the concrete, adding costs to the construction of the building both in terms of material costs and labour costs.
Landing dollies have been also developed for the prior art forms. These dollies are required to be of a substantial height to reduce the distance which the form must be raised to achieve the desired height of the upper deck. Accordingly, the dollies are large and cumbersome. Further, a good number of these dollies are required if the crane waiting time is to be substantially reduced. However, the flying forms still require significant labour to lower the legs, set the jacks and remove the dollies.